On Guemas et al (2013) “Retrospective prediction of the global warming slowdown in the past decade”

I received a number of emails about the newly published Guemas et al (2013) paper titled “Retrospective prediction of the global warming slowdown in the past decade”. It’s paywalled. The abstract is here. It reads:

Despite a sustained production of anthropogenic greenhouse gases, the Earth’s mean near-surface temperature paused its rise during the 2000–2010 period¹. To explain such a pause, an increase in ocean heat uptake below the superficial ocean layer^{2, 3} has been proposed to overcompensate for the Earth’s heat storage. Contributions have also been suggested from the deep prolonged solar minimum⁴, the stratospheric water vapour⁵, the stratospheric⁶ and tropospheric aerosols⁷. However, a robust attribution of this warming slowdown has not been achievable up to now. Here we show successful retrospective predictions of this warming slowdown up to 5 years ahead, the analysis of which allows us to attribute the onset of this slowdown to an increase in ocean heat uptake. Sensitivity experiments accounting only for the external radiative forcings do not reproduce the slowdown. The top-of-atmosphere net energy input remained in the [0.5–1] W m⁻² interval during the past decade, which is successfully captured by our predictions. Most of this excess energy was absorbed in the top 700 m of the ocean at the onset of the warming pause, 65% of it in the tropical Pacific and Atlantic oceans. Our results hence point at the key role of the ocean heat uptake in the recent warming slowdown. The ability to predict retrospectively this slowdown not only strengthens our confidence in the robustness of our climate models, but also enhances the socio-economic relevance of operational decadal climate predictions.

Not too surprisingly ClimateProgress has a post New Study: When You Account For The Oceans, Global Warming Continues Apace about the paper.

The abstract suggests that the tropical Pacific and Atlantic Oceans are responsible for 65% of warming of global ocean heat content for the depths of 0-700 meters since 2000. However, the much-adjusted NODC ocean heat content data for the tropical Pacific (Figure 1) shows a decline in ocean heat content since 2000, and the ocean heat content for the Atlantic (Figure 2) has been flat since 2005.

Figure 1

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Figure 2

The abstract also mentions a new-found ability to predict slowdowns in warming. But the warming of tropical Pacific ocean heat content is dependent on the 3-year La Niña events of 1954-57, 1973-76 and 1998-01 and on the freakish 1995/96 La Niña, Figure 3. And the warming of sea surface temperatures for the Atlantic, Indian and West Pacific oceans, Figure 4, depends on strong El Niño events.

Figure 3

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Figure 4

CLOSING

Can Guemas et al (2013) can predict 3-year La Niñas and freakish La Niñas like the one in 1995/96? Can they predict strong El Niño events, like those in 1986/87/88, 1997/97 1997/98 and 2009/10? Both are unlikely—the specialized ENSO forecast models have difficulty projecting beyond the springtime predictability barrier every year.

FURTHER READING

For further information about the problems with ocean heat content data, refer to the post Is Ocean Heat Content Data All It’s Stacked Up to Be?

And for further information about the natural warming of the global oceans, see “The Manmade Global Warming Challenge.”